/**
 * Copyright (C) 2001-2020 by RapidMiner and the contributors
 * 
 * Complete list of developers available at our web site:
 * 
 * http://rapidminer.com
 * 
 * This program is free software: you can redistribute it and/or modify it under the terms of the
 * GNU Affero General Public License as published by the Free Software Foundation, either version 3
 * of the License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
 * even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Affero General Public License for more details.
 * 
 * You should have received a copy of the GNU Affero General Public License along with this program.
 * If not, see http://www.gnu.org/licenses/.
*/
package com.rapidminer.operator.learner.associations.fpgrowth;

import java.util.ArrayList;
import java.util.List;


/**
 * A frequency stack based on a list implementation.
 *
 * @author Sebastian Land
 */
public class ListFrequencyStack implements FrequencyStack {

	private List<Integer> list;

	public ListFrequencyStack() {
		list = new ArrayList<Integer>();
	}

	@Override
	public int getFrequency(int height) {
		if (height >= list.size()) {
			return 0;
		} else {
			return list.get(height);
		}
	}

	@Override
	public void increaseFrequency(int stackHeight, int value) {
		if (stackHeight == list.size() - 1) {
			// int newValue = value + list.pollLast(); // IM: pollLast only
			// available in JDK 6
			int newValue = value + list.remove(stackHeight);
			list.add(newValue);
		} else if (stackHeight == list.size()) {
			list.add(value);
		}
	}

	@Override
	public void popFrequency(int height) {
		if (height <= list.size() - 1) {
			list.remove(height);
		}
	}
}
